tipping in restaurants, river boat/barge, etc

Of course -- if you are in Europe, use Euros!

We plan to tip in euros. Since the dollar isn't worth as much I'd think it would look "cheap" not to use euros. But that's just my opinion.

You tip in local currency! How would you like it if I tipped you with some left-over Vietnamese dongs? What do you think an American waitress would think if she gots tipped with some Euro cents? She wouldn't know what it is. After all she'd never seen any before. Same with French, German, Dutch, ..., waitress. She would have never seen US cents or dollars before and think you might as well have given her some plastic buttons...

exactly. you're just making them go exchange it. but be careful... it depends on where you're going. some european countries dont tip - or not much. in spain, for example, you'd only tip change (a euro at the MOST) if service is exceptional. otherwise they take offense, as if you're saying that they need your tip bc they dont make enough money. this applies in cafes, restaurants, taxis, everywhere

thank you very much.